The provision of instrumentation for the accurate infusion of intravenous fluids to patients has received substantial attention over the past two decades. Devices for providing controlled gravity flow, as well as flow induced by mechanical pressure, have been provided which consist of two major elements The first is an instrument which the clinician programs with desired flow parameters and which contains electromechanical elements for controlling and monitoring flow. Such instruments ordinarily cooperate with an intravenous tubing set having a sealed fluid path which does not come in contact with the instrument. Typically included in the tubing set is an in-line cassette or other flow element which is positioned in the instrument during use.
The present invention provides a compact pump instrument suitable for wearing by an ambulatory patient, operating with a disposable in-line cassette providing the necessary valving and pumping functions for the infusion of three different fluids along independent flow paths. A device constructed in accordance with the invention is relatively simple and inexpensive, and employs a valving system which is not dependent upon the accuracy of alignment of the disposable cassette in the pump instrument. Despite the compactness of the pump instrument and the small size and simplicity of the disposable cassette, the system constructed in accordance with this invention permits the clinician to input independent flow rates and other flow parameters for three distinct fluids which are pumped along isolated flow paths to the output of the system. The fluids may be pumped simultaneously or sequentially, and the fluid output may be conveyed separately to distinct patient infusion sites, or combined in a single patient line as desired.
The pumping instrument of the invention utilizes a single drive motor for each fluid independently operated to actuate all of the essential pumping and valving actions necessary for accurate volumetric infusion of that fluid. In addition, a single drive is provided to actuate fail-safe shut down valving means of all fluid paths through the system.